Process for treatment of porous materials and product thereof



Patented Mar. 14, 1939 UNITED I STATES PROCESS FOR- TREATMENT OF POROUS MA- TERIALS AND PRODUCT THEREOF Hugh Fleanor Rinpey, Auburn, and Theodore Williams Dike, Seattle, Wash, assignors to I. F. Laucks, Inc., Seattle, Wash., a, corporation of Washington No Drawing. Application September 4, 1937, Serial No. 162,517

6 Claims.

This invention relates to a new process for protective treatment of wood and other porous surfaces and the new products thus created. The principal object is to inhibit raising of wood grain after the final smoothing of the surface by sanding or the like. Another object is to provide a' better foundation for subsequent finishing work. Another object is to increase water, weather and abrasion resistance both by increasing at least the surface density and by simultaneously healing and repairing the minute fractures common in wood surfaces. Another object is to impregnate at least the outer surfaces with fungicides and bind them in protective location so that they cannot subsequently be lost by leaching or evaporation. Another object is to waterproof other porous surfaces such as brick, stone and concrete.

The present application and a companion application Serial No. 162,516, filed simultaneously, refer to treatment of porous surfaces, especially wood surfaces; and in the present case the claims are concerned with the process and products of the treatment, while in the companion case the claims are concerned with the composition.

Since exposure to atmospheric moisture swells dry wood-substance approximately in inverse proportion to the local wood density and since all woods have local variations, they all show some tendency for the grain to expand, while those with extreme density variations are most troublesome, owing to their unequal swelling creating corresponding unevenness of surface. In some of the soft woods, each exposed annual ring shows two distinct bands, one of low density spring wood alongside another of high density summer wood. Such wood surfaces, on exposure to damp air, develop considerable roughness. If then resanded smooth, they will soon get rough again and this is repeated indefinitely. Furthermore, minute fractures already present develop into serious surface checks. The hard woods being of such more uniform texture show far less unevenness of surface, their grain-raising being mostly a mere raising of individual fibers here and there while checking is usually infrequent.

The present process, -while adapted for counteracting such tendencies in all woods, fills a long felt want when applied to the most troublesome kinds. Douglas fir is a wood which shows both grain-raising and surface checking at their worst because the wide growth rings have strongly marked alternate bands of very soft spring wood and decidedly dense summer wood. It is also one of the most extensively used species,

lar tendencies are other softwoods, especially western hemlock, western red cedar, and redwood.

The following description of the specific problems involved and the previous attempts to find their solution will facilitate full and clear dis- 15 closure of the character, scope, and practise of the present invention.

Both fir lumber and plywood are cheap, nationally distributed, and have excellent working qualities, strength and durability. Due to this 90 they have come into widespread use for interior finish, but owing tothe grain-raising defect, and also the checking tendency, such use is attended by much disappointment causing an unfavorable consumer reaction and a great deal of grief to 25 the manufacturers and distributors, restricting the use of the wood much more than is generally realized. These finishing difllculties are of a particularly aggravating and deceptive character, involving a great deal of costly hand sanding on the job, and still worse, the feature that the smoothed surfaces do not stay smooth after finishing. In a few weeks or months the grain rises again and shows through the finish and numerous checks also frequently break through.

In the mill, the finishing lumber is easily surfaced and the plywood machine-sanded to a smoothness which at the moment appears suitable for a good finishing job. Even the lathe checks arefilled up with dust and temporarily invisible. However, the grain rises again quickly, even overnight, and upon arrival on the construction job, regardless of whether that is the next day or after months of passing through the hands of distributors, the surface has become decidedly uneven and looks as if the mill had done a poor job.

The painter on the job makes a few disparaging remarks about the poor quality of mill finish 50 and sets to work to sand it smooth again by hand. If he does this thoroughly for an exacting job, the hand labor is considerable and adds materially to the cost. Everything now seems ready for a first-class finish and if the painter and contractor are unfamiliar with not lookfor further trouble.

The painter now proceeds with the finishing and in a few days turns out a fine looking interior which readily passes the inspection of architect and owner. The workmen are paid and the owner moves in. Up to this stage, beyond the added cost of a lot of seemingly unnecessary hand sanding, there is no cause for complaint. However, after a few weeks or months, the owner begins to notice, especially on the wider surfaces such as door panels, that the finish does not seem so smooth and attractive as he first thought. The suspicion soon becomes a reality and 'a cheap half-finished appearance with pronounced showingof the annual rings and usually a considerable number of surface checks permanently replaces the original attractive smooth finish. The consumer's reaction is one of great dissatisfaction which is conveyed back to the architect, contractor, painter, and mill in a really unjust blame for the inherent grainraising and checking defect of the wood itself.

Such experiences universally repeated for many years have restricted the use of the finishing lumber and plywood, in the aggregate to the cheaper uses which, while involving great volume, are far less than the possible field with such restrictions removed. In the case of fir plywood, production exceeds 750 million square feet per year, most of it receiving a decorative finish of some sort demanding permanent smoothness for full decorative effect.

Efforts to solve both the grain-raising and checking problems have been long continued, varied, and costly. Individual mills have conducted many researches of their own, individual paint manufacturers have worked on the problem and twice it has been put up to the National Paint Manufacturers Association for solution. In addition, countless individual finishing experts have given their best efforts to solve the problem. These efforts have all failed and even the experts with unlimited facilities available have had no better luck than the individual painter.

Aside from the mere question of preventing grain-raising, the same lack of uniform surface fir they do density which causes grain-raising, also subjects these troublesome woods to repeated stresses which tend to disintegrate the surface by opening up checks and greatly reduces weather resistance. Consequently, it is evident that any treatment which permanently inhibits grainraising will also materially improve weather resistance and broaden the field of use especially in out-of-door exposure.

The attempts to inhibit these tendencies have followed traditional lines for first coaters, using thin lead and linseed oil paints, wash coats of shellac or glue size, and light coats of thinned raw or boiled linseed oil or cheap rosin varnish. As regards inhibiting grain-raising none of these were effective and some treatments caused addi tional specific surface roughening due to their application. Furthermore, after resanding and applying the final coats to complete the finish, there was no reduction in the tendency for the grain to ultimately rise and show through. Besides these failures with first coater treatments, many attempts were made particularly on doors, to produce durable enamel jobs by simply using a great number of coats, for instance five or six or even more. It was found, however, that a five coat enamel job on a door, in spite of its perfect appearance after completion, at most only delayed the appearance of the trouble as compared to an ordinary three coat job. In both cases the grain eventually showed through to a disheartening extent and usually some checks appeared.

In accordance with the present invention however, such difiiculties may be overcome; and to the accomplishment of these and related ends, the invention, then comprises the features hereinafter fully described, and particularly pointed out in the claims, the following description setting forth in detail certain illustrative embodiments of the invention, these being indicative however, of but a few of the various ways in which the principle of the invention may be employed.

A study of prior attempts to solve these problems, disclosed certain features that appeared significant. It was noted that the lead-linseed oil first coaters caused local surface roughness through pigment aggregating by capillary attraction around loose surface fibers. We tried eliminating the pigment, and although preventing the initial roughening of the surface this still failed to render the surface resistant to grain-raising when water was brushed on or upon exposure to moist air. Neither the substitution of boiled oil nor the addition of driers improved the resistance. Alcoholic shellac caused a general although less marked raising of the grain similar to water, and after drying and resanding the surface was not resistant. Aqueous glue size was worse because it raised the grain still more due to the water vehicle, required more sanding to smooth down and the final surface was non-resistant. Thin linseed oil base varnishes did not themselves raise the grain but the dried surface was non-resistant. The solids left behind after the drying of the vehicle must be much more water resistant than linseed oil and the vehicle must be of a non-grainraising, non-water-soluble oily class.

We have discovered however, that a thin very penetrating non-water miscible volatile solvent solution of heat polymerized derivatives of tung oil containing as their principal constituent the beta form of eleostearic acid or of its compounds, when applied to smoothed wood surfaces in such a manner that the solids are deposited as an impregnation within the outer layer of cells, particularly the surfacecommunicating cells and fractures and hardened there, inhibits grainraising, greatly reduces checking and has other advantages as well.

Eleostearic acid is the principal fatty acid component of tung oil existing in the raw oil in the liquid alpha form and constituting to per cent of the total. The raw oil containing the alpha acid is a liquid of a relatively low molecular weight, readily air dried and hardened by the usual drying oil oxidizing action. In this form the oil has no value for inhibiting grain-raising any more than has linseed oil. By controlled heating of the oil, the constituent fatty acid is easily changed from the liquid alpha form to the semi-solid or solid gelatinous beta form by polymerization. In this form the oil when properly thinned, is an extremely effective inhibitor of grain-raising and checking. If the polymerization is not carried too far, the thickened or bodied oil is soluble in the usual dry oil volatile solvents and can be air dried both by oxidation and by further polymerization to form very durable water resistant films either alone or more rapidly in the presence of driers.

The heat modified tung oil may be used alone when properly thinned or the raw oil may be modified and the constituent fatty acid heat converted to the beta form in the presence of, or by reactive combination with, a variety of modifiers and reactants and the resulting oil soluble prodnot is also effective. Suitable modifiers include glycerine, other drying oils such as linseed or perilla, semi-drying oils such as soybean and cottonseed, rosin, fossil and other varnish gums and their esters such as ester gum, cumar and indene resins, together with oil-soluble phenolic and alkyd varnish resins. All of these modifiers also have the effect of making the heat conversion of the alpha acid to the beta form proceed more slowly, so that by their use it is easier to polymerize the oil without so much risk of the thickening getting out of control and producing a nonoil-soluble gel which could not be thinned down again. By their use also the solid content of the resulting thinned solution can be varied over a wide range and yet maintain the viscosity constant, a heavier bodied oil derived from longer or more intense cooking naturally tolerating more thinner before the desired viscosity is reached.

In general, these modifiers or reactants may be present in amounts up to about one-third of the tung oil component and good results be obtained from the derived compound in the present process. In the case of linseed oil which is ineffective alone, a mixture of equal parts tung and linseed oil proved effective after heat treatment to polymerlze the eleostearic acid to the beta form. None of these modifiers, however, are effective in the absence of the heat polymerized tung oil. This is surprising in view of the fact that some of them, for instance the oil soluble phenolic varnish resins, have notable water resistance.

Complex resinous compounds of beta eleostearic acid may also be formed by combining it with the resinous reaction product of polyhydric alcohols such asgglycerine and dibasic acids or their anhydrides such as phthalic anhydride. Alone, these latter two components combine to form the pure alkyd resins, and in further combination with tung fatty acid, the latter changes to the beta form and unites with the pure alkyd resin to form the so-called tung oil modified alkyd resins which are available commercially. These latter heat polymerized tung oil derivatives are especially useful in the present process, while in contrast thereto the corresponding linseed oil modified alkyd resins are useless for preventing grainraising. Such resins are usually made from the isolated fatty acid but may also be made from the oil direct.

Thus it appears that the heat polymerized beta eleostearic acid -compounds possess specific properties for the present process and are thereby able to impart their useful effects to the resulting mixture or compound, so as to mask or overcome ineffectiveness of the modifier itself in the absence of the heat polymerized tung oil. Tung oil may also be polymerized to some degree at room temperature by the action of light but this form is ineffective to inhibit grain-raising. It is essential that the oil be heat polymerized to become effective. An effective heat polymerized product however, may be produced either by heat treatment of the oil alone, or in the presence of one or more of the non-reactive modifiers, or in the presence of reactive modifiers such as rosin or an alkyd resin. An equivalent to tung oil is oiticica oil which contains couepinic acid, a geometrical isomer of eleostearic acid, present in the raw oil in the alpha form and similarly convertible by heat polymerization to a beta form having equivalent properties to beta eleostearic acid. From time to time new drying oils, either natural or synthetic of equivalent properties, become commercially available, and the teaching of the present disclosure provides a ready means for any skilled varnish maker to utilize their equivalence for the present process. An instance of such a possible material not now available commercially is Po-yoak oil from Parinarium Sherbroesne which is closely related to oiticica oil and has been suggested as a possible substitute for tung oil in varnish making. All effective forms may therefore be grouped together and designated as heat polymerized derivatives of tung oil.

The method of heat polymerizing the tung oil, with or without modification as outlined above, follows the usual practise of varnish making and will be readily understood by anyone skilled in the art. The oil with or without the modifier, as the case may be, is heated under careful temperature control to between approximately 250 and 310 C. and held at the desired temperature until test shows that the proper body or viscosity has been attained, and in the case of modifiers capable of chemical combination, until the combining reaction has been completed. The material is then thinned with common varnish solvents such as coal tar solvents, hydrogenated naphtha, petroleum thinners, dipentene, mineral spirts, benzol, toluol, turpentine, and the like, during cooling, and is adjusted to the desired viscosity for actual use. Driers are preferably added in the usual way to accelerate the drying out and solidification of the protective solids in the wood.

In order that the material may properly pene trate the surface communicating cells and the fractures and produce both a modification of the outer wood cells and heal together the fractures as distinguished from merely leaving a. varnishlike coating on the surface, it is essential that the material be thinned much more than is required for ordinary varnish. It has been found that best results are generally obtained in the viscosity range of approximately between 50 and 100 seconds (Saybolt Universal) 70 F. By varying the extent to which the tung oil or its reaction product is bodied in the heat treatment as well as the nature of the thinner, a treating solution may be obtained with non-volatile solid content between about fifteen and thirty per cent and remain within the aforementioned viscosity limits. The viscosity range of ordinary varnish generally runs upwards of 300 seconds, commonly about 400 seconds and the solid content 45 to 60 per cent. Ordinary varnishes, owing to this relatively heavy viscosity and high solid content only penetrate a smoothed wood surface such as a sandeclfir plywood panel to an extremely shallow depth, seldom reaching .001 inch and then only in the soft grain, while the hard grain shows no measurable penetration. There is also practically no penetration of the checks or fractures. The deposit is almost wholly a surface film with only an ineffective trace of actual impregnation. With the material of the present invention at the viscosity range between 50 and 100 seconds, the penetration is, on the contrary, deep-seated and rapid, so that a general penetration from .002 inch to .005 inch deep is readily obtained with practically all the solids deposited within the wood and both hard and soft grain effectually modified. In addition, the checks are usually penetrated to their full depth even in the case of a thick face veneer. If the solids are capable of inhibiting grain-raising, this depth of penetration is effective for that objective, while the extremely shallow penetration of the ordinary varnish consistency is not. Simultaneously, the deep penetration of the checks binds them together and heels them up.

In order to reduce the fire hazard, it is preferable to partially substitute inflammable solvents with carbon tetrachloride or other non-inflammable equivalent to brlngthe fiash point up to at least 114 F. A drier, for instance a cobalt drier, is preferably added to accelerate hardening of the deposited solids. An amount on the basis of metal content of between 0.1 per cent and 0.4 per cent is usually sufficient.

The method of applying the protective materials is simple and only requires observance of certain rules. An essential feature to be emphasized is that the treatment be directed toward modifying the outer layer of cells, particularly the surface communicating cells and checks by absorbed deposits of the protective solids as distinguished from merely covering them over with a. surface film. This in rather than on the wood effect is made possible by the thinning to the low viscosity of less than seconds. A desirable viscosity is about 66 seconds for many purposes. Since deep penetration is desired, a moderate rate of evaporation of the vehicle is preferable. Owing to the fact that only the water miscible solvents such as water itself, ethyl and methyl alcohol, acetone, glycerine, etc. have any specific grain-raising effect on wood fibers, while non-water-miscible solvents are free from such effects, the whole range of such vehicles used in thinning varnishes is suitable for the present process and it becoms an easy matter to select or blend them so as to suitably control the rate of evaporation. For example, a convenient thinner is a close out petroleum distillate having a. distillation range between and C. This may be reduced as required with carbon tetrachloride to control the flash point. Solvent compatibility need only be considered where a modified product containing an element of limited solubility is present. Solution is necessary.

The application may be by brushing, dipping, spraying, or any convenient method which permits the uniform application of a sufficient quantity of the liquid to saturate the outer wood cells, particularly the surface communicating cells, to a depth of .002 inch to .005 inch without leaving behind an excess to form a film over the surface. Excess is indicated by shiny varnish-like deposits appearing on the surface of the hard grain. Such excess deposits, while they do not detract from inhibiting grain-raising, indicate waste of material and may cause a new kind of surface unevenness by building up on the hard grain.

Where large quantities of panels must be treated, as in treating plywood immediately after sanding in a plywood mill, machine methods become desirable. Any type of machine which will control the time interval of immersion or application and uniformly remove an undesired excess from the surface will produce satisfactory results. We have quite surprisingly discovered that in treating panels according to this method, they may at once be piled one on top of another and left to dry in that condition and yet without sticking together. This is a remarkably convenient method for handling plywood, and we have found that this close piling permits a more complete and deep-seated impregnation of the wood surface. When the panels are closely piled, the crevices between them immediately become filled with a saturated atmosphere of the solvent trichlorphenol,

which greatly retards drying and so permits more liquid to be absorbed, while sticking together is avoided by the material being exhausted into the wood before the drying is completed. To avoid sticking, the solvents must be such that the solids are not precipitated out of solution before the surface dries.

. The close piling method affords a. useful exception to the rule that the practical upper limit of viscosity is about 100 seconds and of solid content about thirty per cent. It has been found that when close piling is carefully practised, the upper limit of solid content may run as high as forty percent with corresponding increased viscosity and yet have substantially all the material penetrate into fir plywood and still not have trouble from the panels sticking together when the piles are opened up. This is due to the beneficial effect of having the absorption take place while the surfaces are surrounded with a solvent saturated atmosphere. When the surfaces are dried in an unsaturated atmosphere as in the open, then the practical upper limit of viscosity is about 100 seconds and of solid content about thirty per cent. The close piling method thus permits deeper and heavier impregnation than is possible with treatment in the open.

Refined, decolorized creosote oil is readily soluble in the protective liquid and may be substituted for a part of the thinner where it is desired to increase the decay and weather resistance of the treated surfaces. There is also a group of highly toxic phenol substitution compounds which have very valuable properties in protecting wood from decay. The oil soluble members of this group are readily incorporated in the treating solution. Examples are orthophenylphenol, 2-4-5 I chlororthophenylphenol, tetrachlorphenol and pentachlorphenol. Obviously, the presence of such powerful decay inhibiting chemicals uniformly distributed well within the surface skin of the wood and held securely in place by the grain-raising inhibiting and fracture healing solids is acooperative action which tends to greatly improve the outdoor life of such treated wood surfaces. As compared to ordinary fungicidal treatment great advantages are gained in eliminating leaching and evaporation of the fungicides. If the grain-raising inhibiting solid selected for the treatment is a tung oil modified alkyd resin, high values in resistance of the protective solids to the destructive effects of sunlight are also obtained and the effect in the aggregate permits fir plywood, lumber and similar wood surfaces to be produced which have long life under such extreme conditions as exterior exposure in tropical climates. The grain-raising inhibiting solids greatly aid in preventing the formation of cracks by the opening up of checks through which wood decay spores could reach unprotected inner wood, while the highly durable tung oil modified alkyd resin assists further in preventing the protective film forming material from itself disintegrating under the influence of strong sunlight.

The following examples illustrate typical methods of preparing compositions which may be advantageously used to inhibit grain-raising and checking in wood and for the general practise of the present invention in the protective treatment of porous materials.

Example 1 200 c. c. of raw tung oil are placed in a laboratory varnish kettle and heated rapidly to 280 C,

if desired.

The batch is held at that temperature for six to eight minutes, then the heat is withdrawn and the oil cooled rapidly to 200 and c. c. petroleum distillate having a distillation range between 160 and 190 C. are added and the batch cooled to room temperature. A clear'heavy bodied oil is produced. 375 c. 0. additional petroleum distillate and c. c. of carbon tetrachloride are added along with 2 c. c. of cobalt drier. I

The treating solution thus produced has a viscosity of about 66 seconds (Saybolt Universal) 70 F. and a flash point of slightly above 114 F. Oiticica oil may be used in place of all or part of the tung oil in which case the heat treatment must be somewhat increased to get the desired body. Oil soluble fungicides may be incorporated Example 2 c. c. of raw tung oil are placed in a laboratory varnish kettle and heated to 150 C. Fifty c. c. of previously melted water white rosin are then run in and the mixture rapidly heated 'to 300 C. and held at 300 till foaming ceases. The mixture is then cooled and thinned as in Example 1 so as to have a final viscosity of about 66 seconds.

In place of the rosin 20 c. c. of glycerine may be used with 180 c. c. of tung oil, or with 150 c. c. of tung oil the full amount of the rosin may be replaced with any of the following:

Linseed oil Cumarene resin Perilla oil Copal resin Soya bean oil Kauri resin Cottonseed oil Oil soluble pure phenolic resin Ester gum Oil soluble oil modified alkyl resin Indene resin Slight adjustments of the quantity of thinner and drier may be made to suit special characteristics of ingredients and the amount of thickening derived from the cooking. The treating solution made with the rosin as modifier, is especially inexpensive and very satisfactory for treating wood for conditions of moderate exposure and general interior finish. Oil soluble fungicides may be. added if desired.

Example 3 erine, a reaction occurs with the development of considerable foam which can be controlled by adding the glycerine gradually. The kettle is then returned to the heat and the temperature restored to 235 C. in two and one quarter minutes, whereupon 120 grams of phthalic anhydride are added with stirring. Upon this addition the temperature walls somewhat but with strong heating it is brought back to 235 C. in about two minutes. The phthalic anhydride combines gradually with a moderate formation of foam which dies away at the end of about ten minutes cooking. The batch is held at 235 'C. for about twenty minutes with stirring, whereupon it is removed from the heat and thinned with 370 c. c. of petroleum distillate having a distillation range between 160 and C. The

resin is then cooled to room temperature. This gives a heavy bodied plastic tung oil modified alkyd resin containing approximately 50 per cent of solid or non-volatile constituents.

100 c. c. of the above are thinned with 100 c. c. 5 of the petroleum thinner plus 50 c. c. of carbon tetrachloride and 2 c. c. of cobalt drier. The product is a tung oil modified alkyd resin solution very effective in the practise of the present invention in preventing both grain-raising and checking and having in addition the desirable durability features characteristic of, the alkyd resins. Tung ,oil modified alkyd resins of similar properties are available commercially and may be used if desired. Oil soluble fungicides such as phenolic compounds may also be added to give greatly increased weather resistance to the treated products.

If in the above example, the 200 c. c. of tung fatty acid is replaced with 400 c. c. of raw tung oil and the procedure duplicated with the cooking extended to twenty-eight minutes, a grain-raising inhibiting product of quite similar properties is also produced.

When making any of the foregoing examples on a large commercial scale, mass reaction effects require appropriate modification in the conditions which will be readily made by any skilled varnish maker. Obviously the product of any of these examples may be distributed in their concentrated form and thinned by the user as required for wood treatment. All of these solutions form highly water resistant films with excellent penetrating properties highly suitable for the treatment of porous materials.

One of the striking characteristics of Douglas fir, western hemlock, western red cedar, redwood, and similar woods of uneven surface density when treated by the present method is the profound modification of the surface in other respects than the mere inhibiting of grain-raising. Other new properties are:

(a) The whole surface approximates uniform hardness, the soft spring wood portion of the annual rings being now of practically the same density as the summer wood. This is probably due to the thickening of the thin cell walls 01' the spring wood by incrustation with the protective solids.

(b) The surface now takes stain and all forms of finishing coats much better than either the untreated raw wood or the raw wood after treatment with ordinary priming coats. The stained effects owing to decreased absorption are particularly free from harsh contrasts hitherto very troublesome. The grain-raising inhibiting treatment has served the additional purpose of a remarkably effective priming coat, imparting to the surface an ideal degree of tooth or ability to take stain or finish coats. Most of the sanding required with ordinary priming coats is also eliminated.

(c) Partly due to the tough resinous nature of the material and partly owing to the increasedand uniform density of the surface, great resistance to abrasion is obtained. The treated surface will now stand several times as many rubs with an abrasive as before treatment. The protective skin of treated wood cells is very difiicult to wear through, and there is now only a slight tendency for the spring wood to wear away at a faster rate than the summer wood. This greatly improves the weather resistance and general utility.

A further gain particularly important in the 75 portant way to the durability of the treated -plywood. It gives cheap rotary cut veneer much of the advantage of high priced sliced and sawn v treatment with the thin bodied penetrating solution, also deeply penetrates, seals, and to a very considerable extent, heals the numerous fractures or lathe checks which are formed in the veneer by the stresses of cutting. These often run through the whole thickness of a ply and hence communicate to the exterior of the resulting plywood, even when the veneer is laid with the least fractured side out, as is ordinary-practise. Also the removal of some of the outer surface of the veneer in sanding exposes many more of these fractures on the outside. These openings serve as conduits permitting moisture and decay spores to enter the wood, besides increasing the destructive shattering effect of continual moisture changes and being responsible for most of the troublesome checks in finished surfaces. The present treatment penetrates these fractures deeply, seals them up with a tough and highly water resistant film of resinous material and to.

a great extent, binds them together. It has been found that these are normally penetrated to their full depth by the treatment. This healing up of this type of mutilation adds in an imveneer.

(d) The water resistance is high on the treated surface and moisture change in the untreated wood below is much retarded but the surface is not hermetically sealed and still is able to breatheor respond to external moisture changes. The

disintegrating swelling effect of moisture change is thereby markedly reduced, and since the surface fractures are also healed up, much longer life results upon exposure to the weather. wing also to the greatly retardedv moisture absorption, the treated wood does not finally reach so high anaverage moisture content when exposed to the weather and this in turn retards and may even prevent fungous growth which wouldotherwise occur. v r

(e) Further improvement in resistance to weather, sunlight and decay is also obtained when the protective base is a tung oil modified alkyd resin preferably with; added fungicidal phenolic or other antiseptic materials in solution. In such cases the protective elements reach maximum efficiency by being ideally located within rather than upon the wood. Also all surface communicating fractures are deeply penetrated with antiseptic bearing material and then healed up with the antiseptics' permanently bound in by the durable resinous solids. Thus for the firstv time it is possible to protect wood against decay by a cheap method which encloses the wood in a thin and hence inexpensive protective sheath,-

but nevertheless one that retains the antiseptic elements under conditions which prevent evaporation or leaching and resist abrasion.

nation.

This solves one of the most troublesome problems in case of plywood and veneer products, is that the door panels and the like, is much better because varnish, paint and enamel jobs are done without the usual preliminary hand sanding, with less cost, and with assurance that a, fine Job of finishing will remain permanently free from the old trouble of the grain showing through and with a great reduction in surface checking.

A simple accelerated test determines the effectiveness of the treatment and is useful in proving formulae. Pieces of fir plywood are sanded smooth with fine paper, dipped foii one-half minute in the solution, drained on edge and dried for forty-eight hours. The piece to be tested is then placed for one minute as a cover on top of a beaker of boiling water. It is then dried with a towel and tested for inequalities of surface with a surface micrometer. The average inequalityof the surface should not exceed .0005 inch. with ordinary first coaters the inequality will generally 7 be about .0035 inch and often reaches .0050 inch.

Since the touch can detect differences of level as low as .0002 inch and the eye .0005 inch, the gain by permanently restraining the differences down to as little as .0005 inch'is obvious.

Besides the method of treating wood and especially plywood superficially and at atmospheric pressure so as to modify forthev most part merely an outer. skin two to five thousandths of an inch deep, pressure and vacuum impregnation methods, may be used to produce either a more deep-seated treatment or-complete impreg- Non-smoothed surfaces may also be treated. Using preferably the tung oil modified alkyd resin solution of Example 3, with added 011 soluble fungicide, new-products result of. extreme resistance to water, weather, and decay. In such treatment a solution of lowviscosityand solid content is preferable and a-cheap and readily volatile vehicle such as a commercial gasolenel desirable. Impregnation is obtained ,by'apressure treatment preferably with a. warm solution in a retort,

usually without preliminary vacuum, and after draining off the'excess'liquid fromthe retort, a

V vacuum may be drawn and a vacuum condensing system used to recover the bulk of 'thesolvent. Upon drying, the fungicides are neither able to evaporate nor be leached out since the resinous solids hold them securely.

A similar or somewhat thinner fungicidal solution tothat described for the above pressure treatment, may be used'with great advantage for preserving fishnets, sail and tent cloth, insulating board, paper, and similar absorbent fibrous materials. In most such cases simple immersion and airdrying is sufiicient. High values in resistance to decay may thus be obtained at minimum cost through making use of the specific resistance towater absorption imparted by treatment with the heat polymerized tung oil constituents and concurrent values in resistance to water, light, weather, and abrasion obtainable by the use of the alkyd resins together with antiseptic compounds. Other porous materials such as brick, stone, and concretemay be very satisfactorily waterproofed with these solutions, due to their 1. The method of preventing grain raising on the surface of wood cut so as to expose a surface having annual rings exposing alternate bands of hard and soft grain, which consists in impregnating the surface with a thin solutionof heat polymerized eleostearic acid dissolved in a nonwater miscible solvent vehicle, the solid content of said solution beingless than 30% and the viscosity of the solution being between 50 and 100 seconds (Saybolt Universal) 70 F., and penetrating substantially the whole surface to a depth of .002 inch to .005 inch whereby the surface of the bands of hard grain is not substantially coated with the solid contents of the solution.

2. The method of preventing grain raising on the surface of wood cut so as to expose a surface having annual rings exposing alternate bands of hard and soft grain, which consists in impregnating the surface with a thin solution of heat polymerized eleostearic acid dissolved in a nonwater miscible solvent vehicle, the solid content of said solution being less than 40% and the viscosity of the solution being between 50 and 100 seconds (Saybolt Universal) 70 F., penetrating substantially the whole surface to a depth of .002 inch to .005 inch and drying said surface in an atmosphere saturated with the vapors of said solvent vehicle whereby the surface of the bands of hard grain is not substantially coated with the solid contents of the solution.

3. The method of preventing grain raising on the surface of wood cut so as to expose a surface having annual rings exposing alternate bands of 35 hard and soft grain, which consists in impregnating the surface with a thin solution of heat polymerized eleostearic acid dissolved in a nonwater miscible solvent vehicle and including a fungicide, the solid content of said solution being less than 30% and the viscosity of the solution being between 50 and 100 seconds (Saybolt Universal) 70 F., and penetrating-substantially the whole surface to a depth of .002 inch to .005 inch whereby the surface of the bands of hard grain is not substantially coated with the solid contents of the solution.

4. The method of preventing grain raising on the surface of wood cut so as to expose a surface having annual rings exposing alternate bands of hard and soft grain, which consists in impregnating the surface with a thin solution of heat polymerized eleostearic acid dissolved in a nonwater miscible solvent vehicle and including a fungicide, the solid content of said solution be- 1 55 ing less than 40% and the viscosity of the solution being between 50 and 100 seconds (Saybolt Universal) 70 F., penetrating substantially the whole surface to a depth of .002 inch to .005 inch x and drying said surface in an atmosphere saturated with the vapors of .said solvent vehicle whereby the surface of the bands of hard grain is not substantially coated with the solid contents of the solution.

5. A fir plywood panel faced with wood veneer of a species which exposes alternate bands of hard and soft grain and having the property of being substantially resistant to grain raising upon exposure to moisture, the cells of the outer surface of the panel to a depth of from .002" to .005" being impregnated with a water resistant compound having a high content of heat polymerized eleostearic acid and the resistance to the abrasion of soft spring wood grain exposed on the surface being substantially equal to that of the alternating bandstof hard grain, the surface of the bands of hard grain being not substantially coated with the solid contents of the compound and the impregnation being produced by a solution in a non-water miscible solvent having a solid content less than 40% and a viscosity between 50 and 100 seconds (Saybolt Universal) 70 F. whereby the surface is rendered resistant to grain raising by the presence of the compound as an impregnant within the wood cells which form the outer surface.

6. A flr plywood panel faced with wood veneer of a species which exposes alternate bands of hard and soft grain and having the property of being substantially resistant to grain raising upon exposure to moisture, the cells of the outer surface of the panel to a depth of from .002" to .005" being impregnated with a water resistant compound having a high content of heat polymerized eleostearic acid and a fungicide and the resistance to the abrasion of soft spring wood grain exposed on the surface being substantially equal to that of the alternating bands of hard grain, the surface of the bands of hard grain beingnot substantially coated with the solid contents of the compound and the impregnation being produced by a solution in a non-water miscible solvent having a solid content less than 40% and a viscosity between 50 and 100 seconds (Saybolt Universal) 70 F. whereby the surface is rendered resistant to grain raising by the presence of the compound as an impregnant within the wood cells which form the outer surface.

HUGH FLEANOR RIPPEY. THEODORE WILLIAMS DIKE. 

